Autonomic nervous system (ANS (activity and attention has been assessed in children and adolescents with Obsessive Compulsive Disorder (OCD) and in normal controls. We recorded electrodermal activity and heart rate during a rest period, a series of nonsignal tones, and a simple reaction time (RT) task. Attention was assessed by two RT task: 1) Simple RT with constant and variable preparatory intervals, and 2) Simple, choice, and "crossmodal" RT to lights and tones. A major purpose of these projects is to look for ANS and attentional markers of diagnosis and subdiagnosis and to determine how these processes might be related to symptoms. ANS activity was not generally different in OCD children from that in cormal controls. However, more severely symptomatic patients had greater ANS base levels and reactivity than those less seriously ill. A somewhat similar, but not identical, pattern of correlations was observed with the clinical course of the illness as evaluated after a 1-7 year follow up period. Boys with a codiagnosis of Attention Deficit Hyperactivity Disorder (ADHD) showed only minor differences in ANS activity form subjects without tics. We have studied the relationships between metabolites of monoamines (serotonin, norepinephrine, and dopamine), ACTH, and neuropeptide Y measured form cerebrospinal fluid and ANS variables in the OCD group and in boys with disruptive Behavior Disorders. Metabolites of dopamine and serotonin were positively correlated with electrodermal activity in the RT task only in OCD group. ACTH was quite consistently (positively) related to ANS activity during the entire protocol. In general there were diagnostic differences in the observed correlations. The ANS and attention test are being repeated on a new sample of younger boys with ADHD. Exploratory test of children with Elective Mutism have been carried out in order to help determine the nature if this disorder.